OpenImageIO/oiio — pull request #512 by lgritz (2013-02-10 22:08:51+00:00)
Title: Clean up ImageOutput handling of unknown or mismatched data formats

Implement new rule for ImageOutput: if the spec passed to open() has
spec.format == UNKNOWN, then select a default data format for the output
file that is "most likely to be able to be read." Also,
ImageOuput::open() will never fail because a requested data format is
unavailable; a reasonable default will always be chosen.

Along the way, fixed a few buggy behaviors in some of the plugins for
certain format combinations.